class Solution:
    def findRepeatNumber(self, nums: List[int]) -> int:
        nums_set = set()
        for i in nums:
            if i in nums_set: return i
            else: nums_set.add(i)
        return -1
    

if __name__ == '__main__':
    solution = Solution()
    nums = [2, 3, 1, 0, 2, 5, 3]
    print(solution.findRepeatNumber(nums))